#### Combining values

def _alt(items, node):

    items = list(items)

    items.sort()

    try: return items[0][1] # value of lowest-numbered item

    except IndexError: return None # input got removed by e.g. FormatException

funcs['_alt'] = _alt

def _merge(items, node):

    items = list(conv_items(strings.ustr, items))

        # get *once* from iter, check types

    items.sort()

    return maps.merge_values(*[v for k, v in items])

funcs['_merge'] = _merge

def _label(items, node):

    items = dict(conv_items(strings.ustr, items))

        # get *once* from iter, check types

    value = items.get('value', None)

    if value == None: return None # input is empty

    try: label = items['label']

    except KeyError, e: raise SyntaxError(e)

    return label+': '+value

funcs['_label'] = _label

types_by_name = {None: strings.ustr, 'str': strings.ustr, 'float': float}

def _nullIf(items, node):

    items = dict(conv_items(strings.ustr, items))

    try: null = items['null']

    except KeyError, e: raise SyntaxError(e)

    value = items.get('value', None)

    type_str = items.get('type', None)

    try: type_ = types_by_name[type_str]

    except KeyError, e: raise SyntaxError(e)

    null = type_(null)

    try: return util.none_if(value, null)

    except ValueError: return value # value not convertible, so can't equal null

funcs['_nullIf'] = _nullIf

#### Dates

def _date(items, node):

    items = dict(conv_items(strings.ustr, items))

        # get *once* from iter, check types

    try: str_ = items['date']

    except KeyError:

        # Year is required

        try: items['year']

        except KeyError, e:

            if items == {}: return None # entire date is empty

            else: raise FormatException(e)

        # Convert month name to number

        try: month = items['month']

        except KeyError: pass

        else:

            if not month.isdigit(): # month is name

                try: items['month'] = str(dates.strtotime(month).month)

                except ValueError, e: raise FormatException(e)

        items = dict(conv_items(format.str2int, items.iteritems()))

        items.setdefault('month', 1)

        items.setdefault('day', 1)

        for try_num in xrange(2):

            try:

                date = datetime.date(**items)

                break

            except ValueError, e:

                if try_num > 0: raise FormatException(e)

                    # exception still raised after retry

                msg = strings.ustr(e)

                if msg == 'month must be in 1..12': # try swapping month and day

                    items['month'], items['day'] = items['day'], items['month']

                else: raise FormatException(e)

    else:

        try: year = float(str_)

        except ValueError:

            try: date = dates.strtotime(str_)

            except ImportError: return str_

            except ValueError, e: raise FormatException(e)

        else: date = (datetime.date(int(year), 1, 1) +

            datetime.timedelta(round((year % 1.)*365)))

    try: return dates.strftime('%Y-%m-%d', date)

    except ValueError, e: raise FormatException(e)

funcs['_date'] = _date

def _dateRangeStart(items, node):

    items = dict(conv_items(strings.ustr, items))

    try: value = items['value']

    except KeyError: return None # input is empty

    return dates.parse_date_range(value)[0]

funcs['_dateRangeStart'] = _dateRangeStart

def _dateRangeEnd(items, node):

    items = dict(conv_items(strings.ustr, items))

    try: value = items['value']

    except KeyError: return None # input is empty

    return dates.parse_date_range(value)[1]

funcs['_dateRangeEnd'] = _dateRangeEnd

def _namePart(items, node):

    items = list(conv_items(strings.ustr, items))

    out_items = []

    for part, value in items:

        try: slice_ = name_parts_slices[part]

        except KeyError, e: raise SyntaxError(e)

        out_items.append((part, ' '.join(value.split(' ')[slice_])))

    return _name(out_items, node)

funcs['_namePart'] = _namePart